He was stressed now he’s not?
Is the substrate a different color? Is the lighting different? Especially the latter could have a huge difference in color with a different type of bulb.
Could be changes in mood. I’ve heard of them changing when for example you turn the lights down, they can get similar colors. Then when the light turns up, they go back. Has it been changing colors or did it just go to that and stay that color?
So besides the tank nothing changed?its been changing colors randomly